The life cycle of black holes with different light signatures is different than the life cycle of objects with the same light signatures.
The research shows that the widely used "unified model of AGN" that characterizes black holes as all having the same properties needs to be revised.
The study provides answers to a nagging space mystery and should allow researchers to create more precise models about the evolution of the universe and how black holes develop.
The objects have puzzled researchers for over 50 years, according to the paper. We have made a lot of assumptions about the physics of these objects. The properties of black holes that are obscured are vastly different from those that are not.
Black holes are thought to be at the center of nearly all large galaxies. The objects can be heavier than small galaxies.
Researchers have been interested in the light signatures of active galactic nuclei for a long time.
Astronomers realized in the 1980's that light signatures coming from space could be attributed to AGNs. The objects were thought to have a ring of gas and dust around them.
The unified theory of AGNs became popular. If a black hole is being seen through its torus, it should appear faint. It should appear bright if you view it from below or above the ring. The past research used too much data from the less obscured objects and skewed results.
Black holes feeding on space matter is the focus of the new study. The rate of accretion does not depend on the mass of a black hole, but on how obscured it is by the gas and dust ring.
Ryan Hickox is a professor of physics and astronomy and a co-author of the study. The structure and how it is growing are related.
The results show that the amount of dust and gas around an AGN is related to how much it is feeding. Dust and gas can be blown away by a black hole. It is more likely to be unobscured. A less active AGN is surrounded by a denser torus and looks faint.
Ananna said that in the past it was unclear how the obscured AGN population differed from their more easily observable counterparts. There is a fundamental difference between the two populations.
Swift-BAT is a high-energy NASA X-ray telescope. Researchers can use the telescope to look for obscured AGNs.
The research is the result of an international scientific collaboration that has been working over a decade to collect and analyze optical/infrared spectroscopy for AGN.
Ananna said that they had never had such a large sample of X-ray detection. It's a big win for high-energy telescopes.
The paper is based on research done by the research team. A computational technique was developed by Ananna to assess the effect of obscuring matter on the properties of black holes.
According to the paper, by knowing a black hole's mass and how fast it is feeding, researchers can determine when most of their growth took place and provide valuable information about the evolution of black holes and the universe.
Where do black holes come from is a big question in our field. I expect this research to become a reference point for this research discipline because it provides a critical piece that can help answer that question.
The team could look beyond the local universe with future research. The team would like to know how long it takes for AGNs to transition from heavily obscured to unobscured.
More information: Tonima Tasnim Ananna et al, BASS. XXX. Distribution Functions of DR2 Eddington Ratios, Black Hole Masses, and X-Ray Luminosities, The Astrophysical Journal Supplement Series (2022). DOI: 10.3847/1538-4365/ac5b64
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